Process for making high octane gasoline



R. A. FINDLAY 2,656,301

PROCESS FOR MAKING HIGH ocTANEGAsoLINE 2 'Sheets-Sheet 1 oct. 2o, r19:53

Fil-ed Jan; 4, 1950 Oct.,20, 1953 R. A. FINDLAY 2,656,301

PRocEss FOR MAKING HIGH ocTANE GASOLINE Patented Oct. 20, 1953 PROCESS FOR MAKING HIGH OCTAN E GASOLINE.

Robert A. Findlay, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application January 4, 1950, Serial No. 136,772

(Cl. ISG-44.15)

7 Claims.

This invention relates to a process for the production of high octane number gasoline. Some of its specific aspects pertain to the segregation of a light gasoline into cyclic and non-cyclic components by certain combinations of fractional distillation and liquid-liquid solvent extraction. In a preferred modification an isopentanized cyclic high octane number aviation gasoline blending component is produced.

It is of course well known and has been for a long time that the various components of natural, straight run, and cracked gasolines differ greatly in their octane numbers. In general the highly branched parafns are of high octane number as contrasted with lower octane number for the straight chain or slightly branched parains. The olefins are of reasonably high octane number, some having quite high octane numbers, but are not always usable in certain types of gasoline. The cycloparaifins (naphthenes) are all of high octane number and have particularly valuable characteristics for use in aviation fuels in view of superior performance under rich mixture conditions. The aromatic hydrocarbons, e. g. benzene, toluene and various alkyl benzenes found in gasolines, are quite valuable for their high octane number, both in ordinary motor fuels for automobiles and in aviation gasolinas. Segregation o-f the various higher octane number components in various ways, has been suggested, and such materials are ordinarily blended with alkylates and other synthetically produced high octane number materials to give finished aviation gasoline or extremely high octane number motor fuels for automotive use. The various aviation gasoline blends are usually finally mixed with suicient isopentane to give a vapor pressure of about 7 pounds Reid.

Heretofore the principal means employed in obtaining desired separation of components of natural, straight-run and cracked gasoline has been super fractionation which involves the use of a large number of fractional distillation columnsr and associated equipment to make very narrow boiling range cuts, so that the desired components can be separated from the less desired components. While this has found' considerable success, and has been a very valuable process, it is clear that the quantity of equipment needed and the utility load, particularly in view f of the numerous evaporations with subsequent e special uses` However, it has not been generally found of sufficient use to warrant commercialization .in treating gasolines in general, perhaps partly due to lack of solvents having the particular characteristics required for gasoline extraction and also various problems involved in obtaining the desired types of components. The present invention provides a means of obtaining superior high octane number gasoline blends suitable for motor fuel or aviation gasoline use by a novel combination of fractional distillation and liquid-liquid solvent extraction retaining some of the benefits of each and providing'an over-all improvement in the process.

An object of this invention is to produce high octane number gasolines.

Another object is to segregate a light gasoline into its components according to octane number.

Yet another object is to combine fractional distillation with liquid-liquid solvent extraction to produce a high octane number aviation gasoline blending stock from natural, straightl run and/or cracked gasolines.

A further object of the invention is to provide improved solvents for gasoline extractions.

A still further object of the invention is to effect a preliminary fractionation of a light gasoline into two portions, with subsequent treatment of each portion involving liquid-liquid solvent extraction to produce an ultimate blending stock of high octane number valuable for use in preparing aviation gasolines.

Yet another object is to recover an isopentanized aviation gasoline stock directly from a liquid-liquid solvent extraction operation.

Another object of the invention is to produce an isopentane-isohexane'blending stock plus an isopentanized cyclic blending stock from an initial light gasoline whose octane number is not sumciently high for employment of the gasoline per sein aviation fuels.

A further object of the invention is to provide a process for the treatment of gasolines involving aliquid-liquid solvent extraction step Wherein ultimate hydrocarbon products are obtained free of solvent.

` Yet another object is to separate gasoline into its constituents according to octane number using a relatively small amount of equipment and with a small condenser load.

Further objects and advantages of the invention will be apparent to one skilled in the art from the accompanying disclosure and discussion.

Broadly speaking, the preferred process of my invention subjects a gasoline, preferably a light gasoline (by which I mean a gasoline having an end point no-t above about 350 l5'. and which may contain limited amounts of butane but preferably very little or no propane and lighter), which may be either a straight-run, natural, or cracked gasoline or mixtures of same, to a first fractional distillation in which at least one pentane fraction is separated from that portion of the gasoline boiling above normal pentane, i. e. is separated from cyclopentane and heavier. Said portion is essentially composed of the sixcarbon-atom and higher hydrocarbons plus cyclopentane, and is generally referred to herein as a Cs-lcut. This Cs-I- cutY which contains all the cyclic hydrocarbons, i. e. naphthenes and aromatics, present in the initialgasoline, is next intimately contacted with a liquid solvent selected from the group consisting of aqueous methanol and aqueous acetonitrile under conditions effecting a selective solution of the cyclic hydrocarbons in the solvent leaving the noncyclic hydrocarbons undissolved. A feature of the invention in one of its more specific aspects also includes the washing of the resulting cyclicpoor hydrocarbon phase with suicient water to remove residual solvent therefrom, the resulting water being incorporated with the solvent in the liquid-liquid extraction step as will be discussed in detail hereinafter. From the liquid-liquid solvent extraction step there is separated a raiinate phase composed of non-cyclic hydrocarbons and an extract phase composed of cyclic hydrocarbons dissolved in the aqueous solvent. This extract phase is next intimately contacted with a portion of the formerly-separated pentane cut of the gasoline under conditions which effect removal of the dissolved hydrocarbons into a separate hydrocarbon phase producing a solvent stripped of its cyclic hydrocarbon content. From this second contacting step is separated the aqueous methanol or aqueous acetonitrile solvent which is recycled to the primary extraction stage and a hydrocarbon phase which is composed of pentane plus cyclic hydrocarbons. It will be understood of course that in the contacting steps just described the separation is not perfect, i. e. the raii'inate phase from the first contacting step may still contain some cyclic hydrocarbons, and/or the extract phase therefrom may still contain some non-cyclic hydrocarbons. The degree of separation can be chosen at will in accordance with economic requirements, it being well known in the art that complete and perfect segregation of components ordinarily requires so many added contacting phases that same is not desirable and separation of say 80 to 95 per cent of the cyclic hydrocarbon content of the feed to the primary extraction zone is usually adequate. When the initial gasoline feed to the process includes olens as in the case of cracked gasolines, the extraction steps can be adjusted and controlled in such manner that the olens are largely obtained with the extract, or are largely obtained with the raffinate, or are partitioned between to whatever extent is desired, depending on the quantity of olefins, if any, which can be used advantageously in the cyclic blending stock to be made by the process.

The hydrocarbon phase obtained from the secondary extraction step described above contains cyclic hydrocarbons removed from the Ce-lcut in the primary extraction step, and these hydrocarbons make up the high octane number cyclic blending stock which is a product of the process.

4 In certain specific embodiments of my invention this hydrocarbon phase is rst subjected to a fractional distillation to remove pentane therefrom (in the present specification and claims the unmodified word pentane refers broadly to isopentane, normal pentane, or both). In other specific embodiments of my invention, the initial fractional distillation of the gasoline is carried out in such a way as to produce an isopentane concentrate which is used as the pentane fraction employed to wash out of the aqueous solvent in the secondary extraction step the cyclic hydrocarbon content thereof, and the resulting hydrocarbon phase in itself constitutes an isopentanized cyclic hydrocarbon concentrate suitable without further fractional distillation for use as a high octane number blending component of aviation gasoline. Further aspects of different specic embodiments of the invention will be disclosed and explained in detail hereinbelow in conjunction with the description of the drawings.

In the drawings, Figure 1 is a schematic flow diagram of apparatus elements and iiow of materials therethrough suitable for practicing one specific embodiment of the invention. Figure 2 is likewise a schematic low diagram, showing another specific embodiment of the invention. It will be appreciated that the drawing is diagrammatic in nature, and while a few valves and controls considered a part of the invention are shown, numerous auxiliary items of equipment, such as heat exchangers, condensers, valves, and the like, will be necessary but can readily be supplied by one skilled in the art having been given the present disclosure.

In Figure l a gasoline which, if the final blending stocks are used in automotive motor fuels may have an end point of about 400 F. but which if the nal blending stocks are to be used in aviation gasolines should have a lower end point such as about 325 or 350 F., is passed from storage or other source not shown via line IIB into fractional distillation unit I2. While this is shown as a single column, it may in some instances be desirable to carry out this fractional distillation in two or more separate columns with associated equipment in a manner which will 'be understood by those skilled in the art. Fractionator I2 is supplied with an internal heater .I4 or external reboiler at the bottom, and reux 1s supplied to the top of same from line I 6. This initial fractionation is effected so as to take off as a bottoms product a Ce-I- cut which should also contain any cyclopentane present in the feed. This bottoms product is removed via line I8 and is passed via line 2E) into a primary extraction vessel 22, rst passing through a Aheater I9 if required. A C5 cut, which may if desired contain any butane present in the gasoline feed, is taken off overhead from fractionator I2 through line 24, condensed in condenser 26, and recovered via line 28, a portion being returned to the top of the column I2 as reflux through line I6.' This pen'- tane cut should contain at least the isopentane 'content of the gasoline introduced into the process through line I o, and may also contain the normal pentane content thereof. In some instances it may be desired to separate the normal pentane separately, which may be done by recovering it through line 30 either as a side cut from a single fractionator I2, or by the use of an auxiliary fractionator as desired. The further use of the pentane cut in line 28 will be described hereinbelow.

Primary'extractor 22 is shown as a single vertiaccesar calv contact column, which is lled with packing,

bubble trays or other liquid-liquid contacting devices known to the art. However, extractor 22. may take any of the known forms for eiecting intimate contact between two partially immiscible liquids in a countercurrent fashion. The (1e-|- hydroc-arbon cut obtained from. the bottom of fractionator l2 is introduced into extractor 22 near the midpoint as sho-wn, preferably through line oriiices or spray nozzles, while the solvent, either aqueous methanol or aqueous acetonitrile, is introduced into same at a higher point fairly near the top, from line 32. The aqueous solvent is maintained in extractor 22 as the continuous phase While the hydrocarbon is the dispersed phase. Into the bottom of extractor 22 is introduced from line 34 through spray nozzles or the like a portion of the cyclic `hydrocarbons ob#- tained as extract, this portion serving as stripping liquid, reflux, backwash, or enriching liquid, these terms being used synonymously herein, to provide an extract of required purity. In the top extractor 22 a hydrocarbon phase is maintained, the interface 38 between this hydrocarbon phase and the solvent phase being maintained at a constant level by oat 38 connected with liquid level control 40 which actuates a motor valve 42 in the liquid outlet line 44 from the bottom of extractor 22. Into the top of extractor 22 is introduced a small amount of water through line 46. The

quantity of this water is metered 'by now meter 48, and can be controlled automatically at a predetermined rate if desired. Thus-introduced water is caused to contact the hydrocarbon phase intimately and removes therefrom by solution the very small amount of solvent which remains dissolved in the hydrocarbon phase, plus any which still is carried therein in suspension. The resulting water containing dissolved solvent flows downwardly in extractor 22 and joins the solvent phase therein. The resulting washed raffinate is recovered from the top of extractor 22 via line 50. This is a cyclic-poor Cc-lhydrocarbon material of relatively low octane number, although the particular octane number depends largely on the proportion of branched chain to straight chain and slightly branched chain hydrocarbons therein. This material is recovered as a product of the process through line 52, and may be joined by means of line 54 by a portion of the pentane cut obtained from fractionator |2 in line 28. The resulting cyclic-poor material can be used per se for any desired use, blended into ordinary motor fuel if the octane number is not too low, or may be subjected to non-catalytic or catalytic reforming operations to improve its octane number. In the event the pentane cut which is later used in the secondary extractor 56 to be described is isopentane, the rafnnate from extractor 22 will contain some isopentane which may be recovered by fractional distillation as shown in detail in Figure 2 described hereinbelow.

Thesolvent phase from primary extractor 22 is passed vicJ line 44 and motor valve 42 into secondary extractor 55 near the top thereof. This extractor is similar to extractor 22 as described above. Here again the aqueous methanol or acetonitrile solvent is maintained as the continuous phase and the hydrocarbon is the dispersed phase. A hydrocarbon-solvent interface is maintained near the top of secondary extractor 56 by means of oat 58, liquid level control 60 and motor valve 62 interposed in the bottom eflluent line 64 of extractor 56. Into the bottom of secondary extractor 56 is introduced a pentane cut solvent. as its function is to remove from the aqueous methanol'or acetonitrile solvent the dissolved cyclic hydrocarbons. These cyclic hydrocarbons plus pentane wash material or secondary Solvent are recovered as a hydrocarbon phase from the top of secondary extractor 56 through line 84, while the aqueous solvent which has been stripped vof 'its cyclic hydrocarbon content but which still contains some dissolved pentane material is recovered from the bottom of secondary extractor 56 via motor valve 62 and line 64 and is in large part recycled via line 86 and line 32 to the primary extractor 22 for reuse therein.

In the event the pentanecut employed as washing liquid in secondary extractor 56 is normal pentane or is mixed isopentane and normal pentane, it is ordinarily desirable to separate saine from the recovered cyclic hydrocarbons present in admxture therewith in stream 84. Accordingly, in such case this material is passed to a fractionator 88 provided with kettle heater 90. From fractionator 68 the cyclic hydrocarbons recovered by the solvent extraction procedure herein described. are recovered as kettle product via line 92, and the net make of this extract material is pro duced as a high octane number blending stock and passed via line 04 to storage, blending, or direct use as desired. A portion of this stock is passed via line 34 back to the bottom of primary extractor 22 as backwash liquid therein to improve the purity of the extract. The overhead from fractionator is composed of the pentane cut plus the small amount of solvent, i. e. methanol or acetonitrile, which is present dissolved in the hydrocarbon phase recovered from the top of extractor 56 via line 04. The` solvent material in question forms a low-boiling azeotrope with pentanes which is recovered in the overhead product therewith. This overhead product is condensed in condenser 95, a portion is passed via line 98 as reflux to the top of fractionator 88 and the remainder is returned via line 62 to the bottom of secondary extractor 5t for reuse therein as washing liquid or secondary solvent. When the pentane cut obtained from fractionator I2 and used as secondary solvent or washing liquid in secondary extractor 56 is isopentane, fractionator 88 will usually be dispensed with.

The 'water content of the methanol or acetonitrile employed in primary extractor 22 is maintained at optimum values in the process of my invention as will now be described. A portion of the aqueous solvent phase recovered from the bottom of secondary extractor 56 via line te is diverted to line |02 and passed via motor valve |04 and line |05 into a fractionator |00, from the bottom of which water is recovered via line Il@ and from ther top of which the water-free or water-poor solvent is recovered via line ||2, passed through condenser |4, a portion returned to the top of column |08 as reflux via line H5, and the balance passed via line H8 back to admixture withthe solvent being recycled via line 86 to the primary extractor 22. Make-up solvent is added to the system from line |28. The fractionator |08 is provided with a kettle heater such as an internal heater |20. Flow controller |22 is set so that a constant quantity of water is to be withdrawn from the process through line I |0, as detected at orice |24. This quantity is set to be essentially equal to the quantity of water introduced into the top of the primary extractor 22 through line 46 as metered by flow meter 45. A continuous specific gravity recorder-controller |25 is interposed in line 86, or arranged to sample and measure continuously a portion of the material passing through line 86 or a sample thereof in known manner. This controller |25 is set to over-ride the response of ilow controller |22 to orice |24 so as to change the setting of motor valve |04 when necessary to maintain the specific gravity of the solvent in line 85 within a selected range, this gravity being directly related to the water content of this stream. In this manner the water content of the solvent in primary extractor 22 is maintained at the desired value. Suitable values in the case of methyl alcohol are 5 to 20 weight per cent water, preferably 9 to 12 per cent, based on total water-methanol solvent. In the case of acetonitrile, water contents of 3 to 15 weight per cent, preferably 5 to 10 per cent, are preferred.

The embodiment of the invention illustrated in Figure 2 will now be described. Wherever possible, the same reference numerals have been used in Figures 1 and 2 to indicate like pieces of equipment and flow lines. A gasoline, which preferably has been debutanized and cut to an end point of 350 F., is introduced via line l0 into fractionator I2. Normal pentane is removed through line 30. Isopentane is recovered as overhead product through line 24 and is passed via line 25 into the bottom of secondary extractor 55 as wash liquid or secondary solvent therein. The secondary extractor is preferably operated at a temperature within the range of 85 to 100 F. The C6+ cut, which also includes cyclopentane present in the gasoline, is recovered as bottoms from fractionator I2 via line I8, passed through heat exchanger 2| and heater I9, and introduced via line 20 into primary extractor 22 at a temperature `within the neighborhood of 150 to 170 F. mtractor 22 preferably gives about 20 theoretical stages of liquid-liquid extraction. Make-up solvent is added to the system through line |28. The circulating solvent, which is aqueous methanol or aqueous acetonitrile, is heated in heater 75 and introduced via line 32 into the top of primary extractor 22. Reflux liquid, which is a portion of the cyclic hydrocarbon extract obtained by the solvent extraction, is passed via line 34 into the bottom of primary extractor 22 for enriching the solvent therein with cyclic hydrocarbons thus improving the purity of the latter recovered as extract product. The cyclichydrocarbon-enriched solvent is withdrawn from the bottom of primary extractor 22 and passed via line 44, heat exchanger 45 for cooling, and line il into a high point of secondary extractor 55 for removal of cyclic hydrocarbons therefrom by intimate contact of the solvent phase with the isopentane introduced into the bottom of secondary extractor 58 through line 25 as hereinabove described. Secondary extractor 56 preferably gives about 20 theoretical stages of liquid-liquid extraction. From the bottom of secondary extractor 56 the aqueous solvent is withdrawn through line 54 and passed via heat exchanger 45, line 32, and heater i5 into primary extractor 22 for reuse therein.

. It is to be understood that various valves, condensers, fractionator kettle heaters and the like shown in Figure 1 will also be used very similarly in Figure 2, but have been omitted for the sake of simplicity in the drawing and brevity of description.

The hydrocarbon phase recovered from the top of secondary extractor 55 is composed of part of the isopentane introduced into the bottom thereof from line 25, plus essentially all of the cyclic hydrocarbons extracted from the Ce-lcut in primary extractor 22 which have been removed from solution in the aqueous solvent by entry into the hydrocarbon phase in secondary extractor 5B. This phase is recovered as overhead from secondary extractor 56 via line 84, part being returned to primary extractor 22 via line 34 as reflux as described, and the remainder being recovered via line 94 for use per se as a high octane number isopentanized cyclic hydrocarbon concentrate aviation gasoline blending stock.

The raffinate phase from primary extractor 22 contains not only the non-cyclic Cc and heavier hydrocarbons originally contained in the gasoline and which remain undissolved in the solvent in primary extractor 22, but also include appreciable amounts of isopentane lwhich has been carried into primary extractor 22 in solution in recycled aqueous solvent introduced into primary extractor 22 through line 34 from secondary extractor 55. The raiiinate phase referred to is recovered via line 50, passed through heat exchanger 2|, then passed through line |30 into settler |32, where it is allowed to settle at a temperature of 85 to 100 F. Methanol or acetonitrile solvent settled out in settler |32 is returned via lines |34 and 32 into primary extractor 22. Hydrocarbon phase is removed from the top of settler |32 via line |35 and passed into a fractionator |38. In this fractionator |38 a separation is made between the isohexanes and lighter, which of course includes the isopentane in the stream, as an overhead fraction obtained through line Mii, and the heavier hexanes and higher boiling hydrocarbons which are obtained as kettle products via line |42. A suitable cut point between the isohexanes taken off overhead in fractionator |33 and remaining hexanes and heavier taken off as bottoms in fractionator |38 is about 150 F. at atmospheric pressure. The material in line |42 is a paraifinic gasoline, containing all of the 05+ components of the original gasoline feed introduced to the process through line |0 except the isohexanes and the cyclic hydrocarbons. This parafnic gasoline recovered through line |42 may be blended into ordinary motor fuel or may be subjected to catalytic or non-catalytic reforming or other treatments to improve the octane number thereof or convert same to more valuable materials, depending primarily on the proportion of relatively high octane number branched chain hydrocarbons present therein.

'I'he overhead from fractionator |38 is carried via line |40 to a fractionator |46, wherein excess -isopentane is taken off overhead via line |44 and returned to admixture in line 25 with isopentane recovered directly from fractionator I2 via line 24. The admixed isopentane is introduced into the bottom of the secondary extractor for reuse therein as washing liquid. The kettle product of fractionator |46 is termed an isopentanized isohexane fraction, has a very high octane number and high volatility, and is employed as a blending stock for preparing aviation gasolines.

From the foregoing it will be seen that in the embodiment of this invention illustrated in Fig- 9 ure 2, two valuable aviation fuel blending stocks are prepared, viz. an isopentanized cyclic gasoline enriched in aromatics and naphthenes, and an isopentanized isohexane stock rich in high 10i TABLE IH Summary of condenser load [Gallons per hour condensed] octane number parailns of high volatility. As 5 Fxtmtion an example of stream compositions obtainable in carrying out the process of Figure 2, the data Using frsaggw presented in Table I are provided. It will be ap- Fig 2 second. glgd; tion preciated that these are merely in general illussfvyelsgl' Solvent trative, and that the exact quantities of materi- 10 als to be obtained 1n the various streams will vary Extractors None None conslderably dependlng on temperatures, flow Extroetatrippen. None 00, 000 rates, character and proportion of the various iotafger g i r Y types of hydrocarbons, extraction eiiclenclesv of Deieopentenizer.- 0, 210 None the particular equipment used, and the like.' In 15 Tm; 52,380 145,920 Tables II and III are listed corresponding equipment and condenser load requirements, respec- 161mm. tively,and these are also compared with equip- 1. A process for the `production of a high ment and condenser loads for (a) extractlOIl 20 octane number aviation fuel blending stock from effected without use of an lsopentane secondary a light gasoline which comprises subjecting a solvons fooulrmg the dissolved hydfooofbons oo light gasoline to fractional distillation to sepabe distilled out from solvent and raffinate phases rate Same into at least one pentane cui, and a and (b1)O eqfulvalent sepaiaiiotn of feed Compo heavier cut containing any cyclopentane present non os y foo loool dls 11 o lon olono Hofe 25 in the said lient gasoline together with ce and again?, 0f Course th? exact Va1ue-s Wm Vary de' heavier hydrocarbons referred to hereinafter as pending on the particular separatlon to be made. a, 06+ cut, subjecting said C04- cut to liquid- The-advantages 0f my mventwn are Obvlousfrom liquid solvent extraction with a solvent selected these filata#- y f from the group consisting of aqueous methanol W h11e Sllelo and Preferred embodiments of 30 and aqueous acetonitrile under conditions selecthe lnvontlOIl hWe been desollbsd llerem, 1'? W111 tively dissolving in said solvent cyclic hydrocarbe appreciated that other varlatlone may be bons present in said out, separating from said made 111 the apparatus 'and process Wl'hOlli deliquid-liquid solvent extraction a cyclic-poor rafpartlng from the splrlt and scope of the lnvennate phase and a cyclic-rich extract phase, tlon. subjecting said extract phase in a second step TABLE I .y T t 1 Iopen l o a v anes Rec le Iso n- I YC Gallons] eigao I' ggef Make-11p Extract escndy Redux tanlijzeed I'raf' tllizeld wapen' hour tracti" phase primary solvent phase i frgctongasoline cyclic gsglline iso' sccliliary extractor ated from gasoline hexanes solvent gasoline Gasolin e 23,700 l0, 700 -i 42, 000 35, 000 7,000 12,500 4,170 solvent 17 200,027 10 200,000 50 l0 17 lsopentane--. 9,000 0,000 5,000 5,390 5.090 1,000 4,390 4, 010

TABLE II Summary of equipment [Gallons per hour condensed] Extraction Superfractionation Using Secondary Solvent N o Secondary Solvent Fig. 2 i

Number Size Number Size Number Size Extractors:

4Primary.. 3 13it. byvBOft Secondary. 3 --do. Fractionators:

Deisohexanizen.-. 2 11ft.by35t1ays.. 2 l`lft.by35trays 2 12ft.`by'35ttays. Deisopentanizer... 1 5ft.by35trays... None 1 lZItJbyEOtrays. So1ventstrippel'--. None 1 llft-by25tlay5 2f StbY-txays 1` 7ft.by25trays... 2 '10ft.iby30trays.

1` tbyfitleys.

2 5/it,by30trays. 2 ftfbytrays. i ,sftiiyeoiraya 2 l2ft.by35trays.

Total 9vesse1s Gvessels 15 vessels.

11 to liquid-liquid contacting with a hydrocarbon washing liquid at least partially composed of said pentane cut under conditions forming a cyclic-poor solvent phase and a cyclic-rich hydrocarbon phase, and recycling said solvent phase to the first named liquid-liquid solvent extraction step as solvent/therefor, at least the cyclic hydrocarbon content of said last named cyclic-rich hydrocarbon phase from said second liquid-liquid contacting step comprising the aforesaid high octane number aviation fuel blending component product of the process.

2. A process according to claim 1 wherein said pentane cutis essentially isopentane, and the isopentane content of said cyclic-rich hydrocarbon phase is retained in admixture with said cyclic hydrocarbons forming an isopentanized high octane number aviation gasoline blending stock.

3. A process'according to claim 2 wherein said railinate phase is subjected to fractional distillation to separate a Cs and heavier parainic gasoline as bottom product and an isopentanized isohexane fraction as overhead product, and said overhead. product is blended with said isopentanized cyclic-rich blending stock.

4. A process according to claim 3 wherein at least a portion of the isopentane content of said isopentanized isohexane cut is separated in a further fractional distillation step prior to the last said blending and is returned to said second liquid-liouid contacting step as a portion of the washing liquid therein.

5. A process according to claim 1 wherein said pentane cut comprises the total pentane content of said gasoline, said cyclic-rich hydrocarbon phase is subjected to fractional distillation to separate as an overhead fraction pentane in admixture with dissolved solvent as a low-boiling pentane-solvent azeotrope, and said overhead fraction is returned as washing liquid to said second contacting step.

6. A process according to claim 1 wherein said primary extraction zone is maintained at 150 to 170 F. and said secondary extraction Zone is maintained at 85 to 100 F.

7. A process for the production of a high octane number aviation fuel blending stock from a light gasoline which comprises subjecting alight gasoline to fractional distillation to separate same into a pentane and lighter fraction and a hexane and heavier fraction, said hexane and heavier fraction also containing any cyclopentane present in said gasoline and being referred to hereinafter as a Cs-lcut, introducing said Cs-lcut into a primary extraction zone at a point intermediate the ends of said zone, introducing a solvent selected from the class consisting Yof aqueous methanol and aqueous acetonitrile into said zone at a point near one end thereof, maintaining liquid hydrocarbons and liquid `solvent in intimate liquid-liquid contact in said zone under conditions effecting solvent extraction of cyclic hydrocarbons from said Ce-I- out, withdrawing undissolvcd cyclic-poor hydrocarbons from said one end of said zone as a raffinate phase, introducing water into said zone at said one end and intimately contacting same with rainate phase to dissolve and thereby remove solvent therefrom, withdrawing from the other end of said extraction zone solvent including water introduced at said rst end and having dissolved therein cyclic hydrocarbons from said Cs-lout, passing the thus withdrawn cyclic-rich solvent to one end of a secondary extraction zone, introducing a hydrocarbon washing liquid into the other end of said secondary extraction zone, said hydrocarbon washing liquid comprising pentanes and being at least partly the aforesaid pentane and lighter cut separated from said light gasoline by fractional distillation as aforesaid, effecting intimate liquidliquid contact of solvent and hydrocarbons in said secondary extraction rsone, withdrawing from said other end of same a cyclic-hydrocarbon-denuded solvent phase and returning a portion of same to said primary extraction rone as the solvent 4as described hereinabove, withdrawing from said rst end of said secondary extrace tion zone a hydrocarbon phase comprising pentane washing liquid and recovered cyclic hydrocarbons, passing same to fractional distillation and separating same into a pentane overhead fraction and a cyclic-rich Ce and heavier including cyclopentane fraction as a high octane num Iber aviation gasoline blending product of the process, returning a portion of the last said cyclic-rich product to said other end of said primary extraction zone as enriching liquid therein, returning the pentane overhead from the last mentioned fractional distillation step to said other end of said secondary extraction zone as the bulk of said washing liquid, withdrawing the portion of cyclic-hydrocarbon-denuded solvent phase separated from said other end of said secondary extraction zone which is not passed to said primary extraction zone as aforesaid and subjecting same to fractional distillation to remove excess water therefrom as bottoms product and recovering a water-lean solvent as overhead, admixing said water-lean solvent with that portion of solvent phase returned to said primary extraction zone, and controlling the water content of the solvent in said primary extraction zone by controlling the water removal from the last said fractional distillation to equal the water introduced into said one end of said primary extraction zone, the quantity of solvent phase passed to said last named fractional distillation being primarily controlled in response to the quantity of water produced as buttoms product with said primary control being sufficiently over-ridden in response to the specific gravity of the total admixed solvent passing to said primary extraction zone to maintain said specific gravity Within a predetermined range corresponding to an optimum range of water content,

ROBERT A. FINDLAY.

References Cited in the le of this patent UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Jan. 13, 1936 Number Number 

1. A PROCESS FOR THE PRODUCTION OF A HIGH OCTANE NUMBER AVIATION FUEL BLENDING STOCK FROM A LIGHT GASOLINE TO FRACTIONAL DISTILLATIO TO SEPARATE SAME INTO AT LEAST ONE PENTANE CUT AND A RATE SAME INTO AT LEAST ONE ENTANE CUT AND A HEAVIER CUT CONTAINING ANY CYCLOPENTANE PRESENT IN THE SAID LIGHT GASOLINE TOGETHER WITH C6 AND IN THE SAID LIGHT GASOLINE TOGETHER WITH C6 AND A C5+ CUT, SUBJECTING SAID C6+ CUT TO LIQUIDS LIQUID SOLVENT EXTRACTION WITH A SOLVENT SELECTED FROM THE GROUP CONSISTING OF AQUEOUS METHANOL AND AQUEOUS AETONITRILE UNDER CONDITIONS SELECTIVELY DISSOLVING IN SAID SOLVENT CYCLIC HYDROCARBONS PRESENT IN SAID CUT, SEPARATING FROM SAID LIQUID-LIQUID SOLVENT EXTRACTION A CYCLIC-POOR RAFFINATE PHASE AND ACYCLIC-RICH EXTRACT PHASE, SUBJECTING SIAD EXTRACT PHASE IN A SECOND STEP TO LIQUID-LIQUID CONTACTING WITH A HYDROCARBON WASHING LIQUID AT LEAST PARTIALLY COMPOSED AT SAID PENTANE CUT UNDE CONDITIONS FORMING A CYCLIC-POOR SOLVENT PHASE AND A CYCLIE-RICH HYDROCARBON PHASE, AND RECYCLING SAID SOLVENT PHASE TO THE FIRST NAMED LIQUID SOLVENT EXTRACTION STEP AS SOLVENT THEREFOR, AT LEAST THE CYCLIC HYDROCARBON CONTENT OF SAID LAST NAMED CYCLIC-RICH HYDROCRON PHASE FROM SAID SECOND LIQUID-LIQUID CONTACTING STEP COMPRISING THE AFORESAID HIGH OCTANE NUMBER AVIATION FUEL BLENDING COMPONENT PRODUCT OF THE PROCESS. 